Targeted and functional genomics approaches to the mechanism of action of lagunamide D, a mitochondrial cytotoxin from marine cyanobacteria

Lagunamide D, a cyanobacterial cyclodepsipeptide, exhibits potent antiproliferative activity against HCT116 colorectal cancer cells (IC50 5.1 nM), which were used to probe the mechanism of action. Measurements of metabolic activity, mitochondrial membrane potential, caspase 3/7 activity and cell viability indicate the rapid action of lagunamide D on mitochondrial function and downstream cytotoxic effects in HCT116 cells. Lagunamide D preferentially targets the G1 cell cycle population and arrests cells in G2/M phase at high concentration (32 nM). Transcriptomics and subsequent Ingenuity Pathway Analysis identified networks related to mitochondrial functions. Lagunamide D induced mitochondrial network redistribution at 10 nM, suggesting a mechanism shared with the structurally related aurilide family, previously reported to target mitochondrial prohibitin 1 (PHB1). Knockdown and chemical inhibition of ATP1A1 sensitized the cells to lagunamide D, as also known for aurilide B. We interrogated potential mechanisms behind this synergistic effect between lagunamide D and ATP1A1 knockdown by using pharmacological inhibitors and extended the functional analysis to a global level by performing a chemogenomic screen with a siRNA library targeting the human druggable genome, revealing targets that modulate susceptibility to lagunamide D. In addition to mitochondrial targets, the screen revealed hits involved in the ubiquitin/proteasome pathway, suggesting lagunamide D might exert its effects by additionally affecting proteostasis. Our analysis illuminated cellular processes of lagunamide D that can be modulated in parallel to mitochondrial functions. The identification of potential synergistic drug combinations that can alleviate undesirable toxicity may open possibilities to resurrect this class of compounds for anticancer therapy.

The mitogenome of Hydropsyche pellucidula (Hydropsychidae): first gene arrangement in the insect order Trichoptera

We describe the mitochondrial genome of Hydropsyche pellucidula Curtis 1834, which is first described for the suborder Annulipalpia and the first in the order Trichoptera to show a non-canonical gene order. The mitogenome was obtained by de novo assembly of shotgun sequenced total genomic DNA using Illumina Miseq technology, which produced an average coverage of 115× and a minimum coverage of 48×. The mitochondrial genome includes 13 protein-coding genes, 2 rRNAs and 22 tRNAs. The genome is characterized by a rearrangement in the relative position of protein-coding and ribosomal genes. This mitogenome sequence will be useful for studying the family Hydropsychidae, which is commonly used for freshwater pollution biomonitoring.